Installation devices of the type just mentioned can be fastened quickly and simply to electrical adapter apparatus by means of standardized mounting brackets. In switching boards and similar set-ups of the prior art, the mounting brackets are arranged separately from the bus rails which may be present. The installation devices are connccted to each other or to the bus rails by means of connector leads for which separate connector clamps are used for electrical and mechanical connection of bus rails and installation devices.
This type of connection requires not only different parts but corresponding room, particularly when the installation devices fixed to mounting brackets must also be connected to the bus rails through fuses providing the required short-circuit protection. In addition, leading the connections from the bus rails to the fuses and the installation devices involves the danger of mis-connections and mix-ups.